In late December, I downloaded all the software updates available for my mac at the time. After that, practically everything started failing - I couldn't open iTunes at all; it said my built-in camera was in use and I couldn't open iChat, Skype, or Photobooth; Firefox would shut down whenever someone messaged me on Facebook chat; Preview would often (but not always) shut down when viewing a photo; I could open and use Photoshop (CS3), but could not save any changes made to files; and I could not burn DVDs to back up photos - it would begin to burn it, but then eventually say one individual file had an error and the DVD could not be burned. I deleted quicktime and after that, a "checking music library" window would come up when opening iTunes (although it still wouldn't open all the way) and Preview started working a little better, so I knew Quicktime had to be at least one of the problems. I used my computer like this for the next week or two, then decided to try re-downloading Quicktime from the Apple website. Magically everything seemed to be back to normal and working fine again, except I could still not burn a DVD. Besides the DVD burner, everything is working now, but I'm finding more and more often that Firefox and iTunes are freezing. In particular, last night I added a bunch of albums to iTunes, and it never fully added them all, just froze. When I try to reopen iTunes, it keeps trying to add the new songs, but still freezes in the middle, so I can't really use iTunes at this point.